Pelvic inflammatory disease is a major or cause of reproductive morbidity worldwide. Its sequelae include tubal infertility, chronic pelvic pain, recurrent PID and ectopic pregnancy. Douching is a common and possibly modifiable potential risk factor for PID, but a handful of previous studies examining this association are retrospective and conflicting. At the same time, compelling data suggest that douching may alter the vaginal microenvironment, thereby predisposing to bacterial vaginosis and perhaps, resultant PID, but this has not been fully tested. We propose to conduct a large, multicenter, prospective cohort study to examine the independent association between douching and PID and to study the effect of douching on vaginal microbiology. We will enroll 1800 women at high risk for acquiring sexually transmitted infections. Half will be women who report douching consistently at least once per month over the past six months; half will be women who report never douching in the past six months. Enrolled women will be evaluated at baseline by interview for behavioral characteristics related to douching and STD risk and by lower genital tract microbiology for N. gonorrhoea, C. trachomatis, bacterial vaginosis, and concentrations of lactobacillus, anaerobes and facultative bacteria. During 3-4.5 years of follow-up, serial interviews will be completed and self-obtained vaginal swabs assessed for lactobacilli and other vaginal bacteria. The primary outcome of PID (symptomatic endometritis), will be compared between the douching and non-douching groups. We will also compare the following: 1) gonococcal or chlamydial cervicitis at baseline, 2) bacterial vaginosis and semi-quantitative lactobacilli concentration at baseline, 3) change during follow-up in the concentration of lactobacilli (hydrogen-peroxide producing and non-producing), as well as anaerobic and facultative bacteria. Given the paucity of information regarding the relationship between douching and reproductive outcomes, the proposed study is imperative in order to direct future public health recommendations.